The Queen issued a statement expressing her sympathies for the people of the state on December 31, saying then: "I have been following with great concern over the last few days the news of the devastating floods in Queensland. Please extend my sincere sympathies to all the people whose communities and livelihoods have been so badly damaged in this disaster."

The donation follows an earlier expression of sympathy by Prime Minister David Cameron in a phone call to Australian counterpart Julia Gillard.

He told Ms Gillard that the UK stood ready to offer any assistance needed to help with the deluge which has swamped large areas of her country and forced the partial evacuation of the city of Brisbane. It is not thought that Ms Gillard requested any specific help.

Downing Street said: "The Prime Minister offered his deep sympathy on behalf of the British people for those who have died, those who have lost their homes and all those who have been affected by the floods in Queensland.

"He stressed how closely people in Britain were following developments. He made clear the UK's strong support for everything the Australian government was doing and his admiration for the amazing resilience shown by the Australian people.

"He said the UK was ready to offer assistance if that should prove necessary."

At least 25 people have died and more than 50 are missing in Queensland after torrential rains which have drenched the state since November forced rivers to burst their banks, inundating an area larger than France and Germany combined.

State capital Brisbane, Australia's third-largest city with a population of two million, is the latest area affected. There were fears that up to 20,000 homes could be swamped by water.